TORONTO, Nov 23 (Reuters) - The United Steelworkers said on Thursday it reached a tentative agreement with Noranda Income Fund on a new labor deal for 371 striking workers at a zinc refinery in Salaberry-de-Valleyfield, Quebec.

Zinc output at the plant, operated by a subsidiary of global mining giant and trader Glencore Plc, had dropped to 50 to 60 percent of normal operating levels during the strike, which began on Feb. 12.

Typical annual zinc production at the plant is 270,000 to 275,000 tonnes.

Traders have closely monitored the labor dispute at North America’s second-largest refinery as prices for the zinc, used to rust-proof steel, touched decade-high prices.

Workers, who walked off the job over proposed pension-plan changes, will vote on the agreement on Saturday, the union said. Contract details were not disclosed. (Reporting by Susan Taylor; Editing by Peter Cooney)